Showing papers in "Journal of Eukaryotic Microbiology in 1965"

Ultrastructure of Trypanosoma lewisi: Flagellum, Microtubules, and the Kinetoplast

Abstract: SYNOPSIS. With the technique of preselecting pure suspensions of trypanosomes for subsequent electron microscopy and with epoxy resin embedding after glutaraldehyde fixation, we have re-examined the ultrastructure of Trypanosoma lewisi with particular reference to the flagellum and pellicle. The peripheral flagellar tubules exhibit clockwise asymmetry; however, sub-tubule B of the peripheral tubules is divided into a doublet by a diagonally running anti-clockwise arm that originates from the median diaphragm. Projections which seem to be continuous with the counter-clockwise arms extend into a “basket shaped” intra-flagellar structure. This structure, originating distal to the flagellar pocket and running anteriorly within the flagellar membrane, may play a role in maintaining the rigidity of the flagellum. The central flagellar tubules have a double helical substructure and dense cross-striae (diameter 50 A), and are regularly arranged at distances of approximately 250 A. The central tubules arise from separate kinetosomal plates that lie at two different elevations. One central flagellar tubule originates from a flattened kinetosomal plate which makes contact with the peripheral tubules. The other central tubule passes through the flattened plate to fuse with an underlying “disc-like” plate. The primary kinetosome exhibits the uniform triplet pattern of tubules at its most proximal region. A pair of tubules closely associated with one of the triplets represents two of the four subpellicular tubules which penetrate the cytoplasm in the region of the flagellar pocket. Sub-pellicular tubules of dimensions similar to the flagellar tubules form a uniform cytoskeleton in all regions of the cell except in the area of the flagellar pocket. A desmosome-like structure maintains continual cell membrane contact with the flagellum and the pellicle. This structure is designated the attachment zone. The fine structure of the kinetoplast is demonstrated. The dense intra-mitochondrial elements (presumably containing DNA) are actually tubules, embedded in a moderately dense matrix. Morphological observations indicate that this organelle is probably primarily concerned with the ontogenesis of mitochondria, and several mitochondria extend from it into the cytoplasm of the cell.

Pinocytotic uptake and the digestion of hemoglobin in malaria parasites.

Abstract: SYNOPSIS. Electron micrographs of sections of Plasmodium falciparum, P. vivax schwetzi and P. ovale in chimpanzees, and of P. gonderi in mangabeys and P. coatneyi in rhesus monkeys showed that all these malaria parasites feed on their host cell by pinocytosis. As in P. lophurae and P. berghei droplets of host cytoplasm are engulfed by the parasites through invaginations of the plasma membrane with the subsequent formation of food vacuoles. Digestion of the content of the food vacuoles follows two patterns. In P. falciparum as in P. lophurae digestion takes place within the food vacuoles, in which hemozoin, the residue of hemoglobin digestion, accumulates. In P. vivax schwetzi, P. ovale, P. gonderi and P. coatneyi vesicles are pinched off from the food vacuoles and digestion takes place in these small vesicles. As in P. berghei hemozoin is not present in the food vacuole proper but only in the small vesicles, indicating that they are the site of hemoglobin digestion. Malaria parasites are surrounded by two membranes, and they contain all the major nuclear and cytoplasmic organelles present in other cells with the exception of mitochondria, which were found only in P. lophurae and possibly in P. falciparum. All other plasmodia possess instead a structure composed of concentric double membranes. It is assumed that this structure performs mitochondrial functions.

Neustonic Marine Craspedomonadales (Choanofiagellates) from Washington and California

Abstract: SYNOPSIS. Neustonic choanoflagellates can be found in marine tide pools in the San Juan Islands, Washington, and on the Monterey Peninsula, California. Several marine photo-synthetic Chrysophyceae (in the Pedinellaceae), which also occur in these regions, have a basic structure so similar to choanoflagellates that this family is placed in the Craspedomonadales. In pointing out this relationship, the derivation of the Craspedomonadales from pigmented Chrysophyceae is strongly indicated. In addition to the naked choanoflagellates, which are placed in the Codonosigaceae, these organisms produce loricae of two different types: 1) loricae possibly of cellulose and without visible structure in the light microscope (Salpingoecaceae), 2) loricae composed of silica strands, sometimes forming a mesh with large open spaces (Acanthoecaceae). Members of the latter family seem to be confined to a marine environment and are a prominent part of this investigation. Examination of several species with the electron microscope has revealed interesting details of lorica morphology that are not visible with the light microscope. Several new combinations of taxa are proposed in addition to new taxa, including 4 new species of Salpingoeca, 3 new species of Diploeca and 4 new species of Pleurasiga. Three new genera are described, Ellisiella gen. nov., Acanthoecopsis gen. nov., and Sportelloeca gen. nov.

The Morphology of Blepharisma undulans Stein

Abstract: SYNOPSIS. Electron-microscope studies have revealed the ciliature and infraciliature of Blepharisma undulans to include tubular filaments about 24 mμ in diameter. As these filaments pass from the kinetosomes into the surrounding cytoplasm they appear to divide into double helical subfilaments, each with a diameter of about 12 mμ. In the somatic region the ciliary rows are composed of series of paired kinetosomes. Connected with the anterior member of a pair are the cilium and transverse filaments, the posterior member giving rise to the posterior kinetodesmal fiber. From between the two kinetosomes arises the anterior kinetodesmal fiber. The kinetodesmal fiber system is associated with the subpellicular fibril system which lines the area just beneath the pellicle of the animal. In the oral region a series of these filaments extends from the proximal portion of the adoral zone of membranelle kinetosomes into the cytoplasm. They traverse the oral area to connect with the undulating membrane on the right margin of the mouth. Also present are fibers comparable to the kinetodesmal fibers and transverse fibers of the somatic region. The functional significance of this system is discussed. The nucleus and nuclear and cytoplasmic inclusions are described, including pigment granules, storage products, the Golgi apparatus, mitochondria and vacuole systems.

Cultivation of three species of Theileria in lymphoid cells in vitro.

Abstract: SYNOPSIS. The intralymphocytic stages of Theileria parva, T. lawrencei and T. annulata have been cultivated for several months in tissue cultures of bovine lymphocytes associated with baby hamster kidney cells. In established cultures the theilerial particles multiplied at about the same rate as the host cells, the percentage of infected cells and the mean number of parasite particles per cell remaining nearly constant. During mitotic division of the host cell the theilerial body becomes closely associated with the spindle fibres and is pulled apart and distributed to both daughter cells in late anaphase. The single theilerial particles (chromatin) within the theilerial body divide by binary fission; their division is not synchronous with that of the host cell.

Laboratory Experiments on the Life Cycle and Ecologic Controls of Rosalina globularis d'Orbigny

Abstract: SYNOPSIS. The life cycle of R. globularis is shown to include a Tretomphalus stage identified as T. bnlloides. The life cycle is further complicated by successive asexual division producing typica1 agamonts. A brief synonymy is given for the genus. Basic experiments with light and substrate variation have shown no direct response.

Cytological Observations on Two Planktonic Foraminifera, Globigerina bulloides d'Orbigny, 1826, and Globigerinoides ruber (d'Orbigny, 1839) Cushman, 1927*†‡

Abstract: SYNOPSIS. Globigerina bulloides and Globigerinoides ruber, two pelagic foraminifera from the North Atlantic, were fixed in modified Zenker or Bouin solutions directly after collection and studied cytochemically. They have two unusual organelles: a vesicular system and an organelle provisionally named a “cryptosome.” The vesicular system occurs chiefly in the newest formed chambers and consists of a pair of intertwined tubules with helical fine structure which terminate in a bouquet of approximately 20 vesicles or loops. The function of this system is unknown. The detailed morphology of the vesicular system is different in each species. The cryptosome is a structure which varies greatly in its morphology. It is better developed in G. bulloides than it is in G. ruber. At times a cryptosome may occupy up to 2/3 of the protoplasm of a chamber. In Himes-Moriber-stained preparations crypto-somes stain with naphthol yellow S and contain within them an azure A-Schiff staining spongy reticulum. Both of the pelagic foraminifera studied are heterokaryotic. Agamonts of G. ruber may have a graded series of nuclear sizes but those of G. bulloides typically have a single somatic nucleus. The zooxanthellae of G. ruber are similar to Symbiodinium microadriaticum and may collectively occupy almost 4/5 the volume of a chamber.

Studies on Feeding and Digestion in Protozoa. VII. Ingestion of Polystyrene Latex Particles and its Early Effect on Acid Phosphatase in Paramecium multimicronucleatum and Tetrahymena pyriformis

Abstract: SYNOPSIS. Food vacuole-free P. multimicronucleatum and T. pyriformis readily ingest non-nutritive Dow polystyrene latex particles (PLP) and form vacuoles containing PLP at a rate comparable to the formation of vacuoles containing bacteria. The particles aggregate within the vacuoles and are egested as balls of the size of the vacuoles. PLP containing vacuoles rapidly acquire acid phosphatase activity, which is demonstrated by histochemical (alpha-naphthyl phosphatehexazonium salt or lead phosphate) methods as a peripheric staining. The total activity of the cell does not significantly change as a consequence of PLP uptake as suggested by the histochemical preparations and confirmed in T. pyriformis by measuring the splitting of p-nitrophenyl phosphate at pH 5. Accordingly, no selection between nutritive and non-nutritive particles could be revealed. The vacuole formation is induced by the mechanical action of the particles. The appearance of acid phosphatase activity in the vacuole seems to be dependent on the vacuole formation and not on its content. This early appearance of activity is due to a redistribution of the preexistent activity.

Preparation of Fatty Acids Labeled with C14 from Ochromonas danica

Abstract: SYNOPSIS. Labeled fatty acids were produced by adding 10 mc acetate-1,2-C14 to cultures of Ochrosonas danica, with a recovery of 21.4% of the radioactivity as mixed methyl esters. Individual esters, or mixtures of isomers, were isolated in amounts between 2 and 200 mg by liquid-liquid chromatography followed by gas-liquid chromatography. Several esters, including Δ8,11,14-C20, Δ5,8,11,14,17-C20, Δ7,10,13,16-C22 and Δ4,7,10,13,18-C22 were obtained pure. Linoleate and arachidonate contained not more than 4% isomers; isomerism was more pronounced with C18:3 and C20:2. The effect of different culturing conditions on fatty acid yield, composition and incorporation of C14 was explored. The radioactive level of acids from the preparative run varied within a factor of 3, the average being about 1 μc/mg. All analytical and preparative procedures are described in detail and discussed.

Two New Species of Plistophora (Microsporidea) from North American Fish with a Synopsis of Microsporidea of Freshwater and Euryhaline Fishes

Abstract: SYNOPSIS. Two new species of Microsporidea, Plistophora salmonae from steelhead and rainbow trout (Salmo gairdntri) and Plistophora crpedianar from gizzard shad (Dorosoma cepedianum) are described. Schizonts to spores of P. cepedianae were found at one time within the same cyst, while only sporonts and spores of P. salmonae were found within the cyst. An illustrated synopsis of the known Microsporidea of freshwater and euryhaline fishes is given.

Infection of alga-free Paramecium bursaria with strains of Chlorella, Scenedesmus, and a yeast.

Abstract: SYNOPSIS. Twenty-one different stocks of Paramecittm bursaria, belonging t o 4 separate varieties (syngens), whose endosymbiotic chorellae had been removed, were tested for reinfection by several strains of Chorella, some previously isolated from P. bursaria, and others free-living. In addition, infection of P. bursaria by a single strain of the green alga Scenedesmus sp., and an unidentified strain of yeast was attempted. Most combinations involving Chlorella yielded infected paramecia, and all those with Scenedesmus or the yeast did so. The failures with Chlorella were attributed to low infectibility of the stocks of Paramecium concerned, rather than to inability of the Chlorella to survive inside the paramecia. Little evidence was found that the strains of P. bursaria differed genetically in ability to maintain the symbiotic organisms.

Studies on Myxosoma cartilaginis n. sp. (Protozoa: Myxosporidea) of Centrarchid Fish and a Synopsis of the Myxosoma of North American Freshwater Fishes

Abstract: SYNOPSIS. Myxosoma cartilaginis n. sp. is described from the cartilage of Lepomis macrochirus (bluegill), L. cyanellus (green sunfish) and Micropterus salmoides (largemouth black bass). The development of the parasite is described from naturally infected fish which were held in spore-free water after infection. The sporoplasm invades cartilage, and becomes a multi-nucleate trophozoite which forms pansporoblasts, each of which produces 2 to 4 spores. The first spores appear in 7 weeks. The histopathology in the above fish consists at first of little cellular reaction, but after 4 to 5 months epithelioid granulomas appear around some of the spore masses. Cartilage liquefaction is present around the parasites for at least 5 weeks. Eosinophilic globules are present in cartilage cells adjacent to the lesions. Diffuse infiltration of the spores from the lesions is described. Of 24 chemicals tested for polar filament extrusion, potassium hydroxide gave the best results. An illustrated synopsis of the Myxosoma of North American fishes is given. Included is some additional information and illustrations of M. hoffmani Meglitsch, 1963. Also included is a table showing the hosts, site of infection, geographic location, spore and polar capsule sizes.

Pigments of blepharisma undulans compared with hypericin.

Abstract: SYNOPSIS. An analysis of the pigments from the protozoan Blepharismn undtulans is reported. Methods of isolation and separation by paper chromatography are described. along with subsequent spectrophotometric and chemical analysis. Since the two major pigments were available only in amounts insufficient for thorough chemical analysis, these pigments were compared with the known pigment hypericin. Although similarities in the visible spectra indicate that the B. unduluns pigments possess the same mesodianthrone structure as hypericin, infrared spectra and chemical reactions disclose differences in the position, and possibly in the number, of the functional groups. A tentative structure is proposed.

Growth of Prymnesium parvum in the dark; note on ichthyotoxin formation.

Abstract: SYNOPSIS. For the first time the chrysomonad Prymnesium parvum was grown in the dark; glycerol was necessary and could not be replaced by any other metabolite tested. The dark-grown cultures, as compared to light-grown ones, atteined an almost 2-fold optical density per cell number, caused possibly by a partial pigment-bleaching in the light or a higher pigment formation in the dark. Ichthyotoxic activity of Prymnesium cultures was greater for the dark-grown cultures in which no photoinactivation of this toxin occurs. Therefore light is not required for synthesis of this toxin.

The Infraciliature and Argyrome of Opisthonecta henneguyi Faureé‐Fremiet

Abstract: SYNOPSIS. Silver stains of the free-swimming sessiline peritrich Opisthonecta henneguyi reveal the adoral infraciliature as the bases of two membranes, a haplokinety and a polykinety, which diverge at the buccal overture and spiral down the infundibulum to end at the cytostome. A second polykinety parallels the adoral polykinety in the oral half of the infundibulum, and the two form a peniculus. The haplokinety appears as a single row of kinetosomes, the adoral polykinety as a series of transverse rows of three kinetosomes. The peniculus is six kinetosomes in width. The electron microscope shows that the haplokinety is a double row of staggered kinetosomes. Only the external row bears cilia. The polykinety is a complex ciliary membrane, three kinetosomes wide. The three kinetosomes are connected with one another by fibrous bundles passing beneath them. They are linked orally and apically into longitudinal rows of thick, zig-zag, fibrous connections. The kinetosomes of the internal longitudinal row are attached by a dense fiber to a strand of fibrous material interrupted at regular intervals by dense nodes. A section of the wall of the infundibulum is thrown up into longitudinal folds with tubular fibrils running parallel to the folds. These structures, the crests, appear to continue into the cytopharynx. Beneath and around the adoral and infundibular infraciliature and the crests is a fibrous matrix with dense nodes, resembling the reticulated infundibular fiber described by Fauree-Fremiet. The trochal band in silver stains appears as short diagonal rows of kinetosomes. The electron microscope shows 5 to 7 kinetosomes per diagonal row. The kinetosomes of the diagonal rows are linked to thick dense rods which originate just above the trochal band and continue antapically past the kinetosomes for a distance of 10 to 15 μ. The kinetosomes are joined to one another by fibrous strands and each is also connected by a dense fiber to the diagonal rod to its left. Running below the kinetosomes and at right angles to the rods is a system of striated fibers. At the aboral end of the body, a ring, 2 μ in diameter, of argentophilic granules is shown by the electron microscope to be a small circle of kinetosomes. Sessile stages have not been reported for Opisthonecta. The aboral ring is probably a vestigial or non-functioning scopula. The argyrome is represented by circular striae around the body. Each stria bears argentophilic dots on either its apical or its antapical side. Electron microscopy reveals that these dots are pores in the cuticle. The striae themselves may be points of adhesion between the inner cuticle and the outer cuticle, or ridges of cytoplasm between flattened alveoli of the inner cuticle. A dense fiber runs below and parallel to each stria. Opisthonecta shows at least three different kinds of ciliary membranes. Some speculations are offered on the taxonomic affinities of peritrichs based on their infraciliature.

Some Biochemical, Cytological, and Morphogenetic Comparisons Between Astasia longa and a Bleached Euglena gracilis*

Abstract: SYNOPSIS. The relationship between Astasia longa and a streptomycin-bleached strain of Euglena grocilis has been examined by several criteria. The organisms differ in their sensitivity to actinomycin D and 8-azaguanine in their ability to incorporate C14-labeled leucine, and in their sensitivity to a new antibiotic called primycin. Euglena forms an induced acid phosphatase when grown in phosphate-deficient medium, but Astasia does not. On the basis of these and other differences, it is suggested that these two organisms are separate genera. Understanding of cell division in these cells has been increased by discovery of an array of tubular fibrils corresponding to a spindle apparatus in the nucleus of a dividing Astasia. This finding, plus the observation that presumptive pellicle complexes are formed during prophase, clarify the fission mechanisms in these organisms.

The Fine Structure of Two Archigregarines, Selenidium fallax and Ditrypanocystis cirratuli

Abstract: SYNOPSIS. In S. fallax and D. cirratuli the pellicle is thrown into longitudinal folds. The pellicle consists of 2 membranes, one 3-layered, the other 5-layered. Sub-pellicular fibrils, each about 23 mμ in diameter run along the pellicular folds. Pellicle and sub-pellicular fibrils together form the mechanism by which Selenidiids move. The undulating membranes of D. cirratuli are enlarged pellicular folds, the tips of which are packed with fibrils. The light ovoid patches seen in thin sections are sections through regions which contain a form of glycogen in the living animals. Typical mitochondria are absent. Objects described as lipochondria have a regular distribution at the bases of the grooves in the pellicle and are probably formed from the inner components of the pellicle.

The Effects of Heat and Cold on Cellular Development in Synchronized Tetrahymena pyriformis WH‐6*

Abstract: SYNOPSIS. Experiments were performed to ascertain the effect of heat and cold on oral and micronuclear development in synchronized Tetrahymena pyriformis WH-6. The developing oral primordium becomes insensitive to cold sometime during stage 2. Cold shocks cause the reversion of many stage 2 primordia to stage 1. Cells so affected are set back in division. The delayed division is always asynchronous. When heat shocks are applied prior to late stage 4, the developing primordium will regress. High temperature shocks applied at later stages permit continued development. However, when the cell begins to cleave at the high temperature, division is frequently arrested and the new oral areas regress. Subsequent cell separation is greatly delayed and asynchronous. Heat and cold affect the micronucleus in the same way. Both agents prolong the arrest of mitosis brought about by the synchronizing treatment. A temperature shock is ineffective if applied after there is a space completely separating the chromosome groups, so that mitosis is completed in the presence of the agent. Bimicronucleate chains result in those cases in which division is arrested by heat shocks. It is suggested that the different phases of sensitivity to heat and cold may reflect different types of syntheses necessary for development of the oral primordium. Division arrest and subsequent oral replacement might possibly be related to high temperature induced changes in the physical state of the ciliate cortex.

An Unusual Pattern of Tritiated Thymidine Incorporation in Euglena

Abstract: SYNOPSIS. Thymidine-methyl-H2 is incorporated into the cytoplasm of Euglena. The label is non-nuclear and not in DNA; evidence for its presence in RNA and protein is presented. Only Euglena which maintain the potentiality to develop chloroplasts show this incorporation; it was not observed in streptomycin. uv, benadryl, O-methyl threonine or heat “bleached”Euglena, nor in Astasia longa. Preliminary incorporation experiments show that exogenous pyrimidines are not utilized as nucleic acid precursors in Euglena in general. However, the tritiated purines are incorporated into DNA and RNA. The use of thymidine to localize DNA autoradiographically in Euglena is completely excluded.

Inhibition by chloramphenicol of chlorophyll and protein synthesis and growth in euglena gracilis.

Abstract: SYNOPSIS. Chloramphenicol inhibits growth of Euglena gracilis. It also interferes in the “greening” process by inhibiting protein synthesis (measured by leucine uptake), but RNA synthesis is essentially unafiected. The antibiotic acts on all cell fractions, but prefermtially inhibits the synthesis of plastid protein. Inhibition of chlorophyll synthesis is transitory and does not affect the self-reproduction system for chloroplast formation.

The Genus Lagenophrys Stein, 1852 (Ciliata, Peritricha) on Australasian Parastacidae

Abstract: SYNOPSIS. A survey of the genus Lagenophrys Stein, 1852 (Ciliata, Peritricha) on freshwater crayfish (Parastacidae) revealed a wide range of new species in Australia and New Zealand. Fourteen new species are described. L. seticola sp. nov. is close to L. vaginicola Stein. L. spinosa, L. bispinosa, L. latispinosa, L. communis, L. occlusa, L. lawrii, L. lingulata spp. nov. form one species group. L. willisi, L. rugosa, L. darwini, L. deserti, L. ditngogi and L. engaei spp. nov. form a second group distinguished by characters of the lorica, lorica mouth and macronucleus. Nenninger's classification of degree of specificity of commensal-host relationship is applied to the whole genus and expanded in the light of the Australian material. The zoogeographic problems resulting from the specificity of Lagenophrys and the limited range of some of its hosts are indicated.

Effect of Nitrofurans on the Chloroplast System of Euglena gracilis

Abstract: SYNOPSIS. Twelve derivatives of 5-nitrofuran were tested on Euglena grarzlis. All rendered the organism permanently apoplastidic and, at somewhat higher concentrations, killed. The furan analogues of 3 of these compounds had no effect on the chloroplast system and were less toxic than the nitrcfurans. Low concentrations of nitrofurantoin and nitroiuraldehyde inhibited formation of chlorophyll when etiolated cells irere illuminated. Exposure of euglena to low concentrations of these agents for about 2 generation times. followed by plating on drug-free mediurn. resulted in a high proportion of bleached colonies. It is theretore concluded that the nitrofurans induce apotplastidy by causing permanent damage to the chloroplast system rather than by inhibiting its replication temporarily. Since one of the nitrofurans which was found to bleach euglena, NFT–3-amino-6[-2-(5-nitro-2-furyl) vinyl]-1,2,4-triazine–is known to cause specific inhibition of DNA synthesis in bacteria, nitrofurans may perhaps bleach euglena through selective damage to chloroplast-DNA or to the DNA-synthesizing system of the chloroplast.

A Proposed Organization of the Genus Blepharisma Perty and Description of Four New Species

Abstract: SYNOPSIS. The following four subgenera. I based chiefly on the form of the macronucleus, are proposed for thr genus Blepharisma Perty 1852: 1) Compactum, having a single compact interphase macronucleus. Type species B Compactum hyalinum Perty. 2) Filijormis, having a vermiform or tubular elongate interphase macronuclcus. occasionally doubled or even fragmented in individuals. Type spcies B. (Filiformis) intermedium Bhandary. 3) Blepharisma, having an interphase macronucleus with two or more nodes usually connected by a very thin strand between the nodes. Type species B. (Blepharisma) Perisicinum Perty. 4) Halteroides, having an interphase macronucleus in two nodes connected by a thick strand. Type species B. (Halteroides) tropicum Bhandary. Differences between the subgenera also can be found in the size, pigmentation, presence or absence of cysts and conjugaion 26 species are presented. While integradations between the subgenera and species exist, it is felt that separation of the four groups is warranted and may indicate possible evolutionary trends within the genus.

Nosema sp. (Microsporida, Nosematidae) in the Musculature of the Crab Callinectes sapidus*

Abstract: SYNOPSIS. A species of Nosema parasitizing the skeletal musculature of the crab, Callinectes sapidzrs Rathbun in the Patuxent River and Chesapake Bay, Maryland, is reported. Spores, in life, are ovoid and measure 2.2 μ by 1.7 μ When stained they are about 1.7 μ by 1.2 μ They closely resemble those of N. pulvis Perez. 1905, in the muscles of Carcinides maenas (L.) but may he slightly larger Lysis of muscle fibers acoompanying heavy infection was noted, but the impontance of the parasite as a mortality factor in crabs is unknown.

The relationship between arginine, citrulline and ornithine in Tetrahymena pyriformis.

Abstract: SYNOPSIS. Studies on the metabolism or arginine, citrulline, and ornithine by Tetrahymena pyriformis confirmed that these compounds do not participate in a urea cycle in this organism. No evidence for the enzymes of the cycle or for the presence of urea or urease was found. However, conversion of arginine to ornithine takes place. This system consists of two enzymes, arginine desimidase and a citrulline-hydrolyzing enzyme. This is different from the arginine dihydrolase enzymes reported for bacteria and yeast, since no labile phosphate is produced in the conversion of citrulline to ornithine. The enzyme responsible for the latter conversion was purified 44-fold. The pH optimum of the enzyme, its substrate specificity, and the effect of inhibitors on its activity were investigated. The enzyme appears entirely hydrolytic in nature.

Fine structure of developing and mature trichocysts in frontonia vesiculosa.

Abstract: SYNOPSIS An electron microscope study of regenerating trichocysts in Frontonia vesirztlosa showed that these organelles oripnate from primordial, membrane-limited vesicles which appear randomly in the endoplasm The characteristic pattern of development leading to the first definitive organization of the trichocyst involves the elaboration of the amorphous intravesicular substance into a series of closely packed fibrous sheets These densely staining elements, laid down in two dimensional arrays, constitute the fundamental plan upon which the various structural subdivisions of the organelle are subsequently formed Maturation involves, however, the re-transformation of the distinctly fibrillar pattern of the body into a homogeneous, structureless matrix The mature trichocyst, consisting of the tip, cap and body, is a pyriform structure bounded by a thin external membrane which is continuous with the pellicle Extrusion of the organelle results in the transformation of the homogeneous tip and body into a slender shaft with transverse striations having a familiar periodicity of about 560 A During discharge the entire organelle is ejected, but the cap does not participate in the formation of the shaft Elementary units of 120A and 250 A periodicities are also described in intracellularly discharged trichocysts These observations are discussed in relation to current theories on the nature of the extrusion process The endoplasmic origin of trichocysts in Frontonia does not support the classical theory of the morphogenetic pluripatency of kinetosomes insofar as i t relates to the direct derivation of these organelles from pre-existing ciliary basal bodies

A Dinoflagellate with Characters of Gymnodinium and Gyrodinium

Abstract: SYNOPSIS. An organism was isolated which in the first instance appeared to be Gymnodinium mirabile and in subsequent cultures took on characteristics similar to those of Gyrodinium fissum. It is not known at present whether the pleomorphism exhibited by this strain is frequent among the naked flagellates, but this finding raises the question of whether naked dinoflagellates can be identified by examination of collected samples, whether living or preserved, or whether culture studies are necessary for all such identifications.

Paranophrys marina n. g., n. sp., a New Ciliate Associated with a Hydroid from the Northeast Pacific (Ciliata: Hymenostomatida)*

Abstract: SYNOPSIS. The ciliate, Paranophrys marina n. g., n. sp., is described from a marine hydroid, Plumularia sp., collected in the San Juan Archipelago, Washington. Morphological studies were made on specimens treated with the Chatton-Lwoff silver impregnation technique. Particular attention is given to the infraciliature of the buccal apparatus and its importance in generic and familial assignment within the order HYMENOSTOMATIDA.

The fine structure of axenically-grown trophozoites of Entamoeba invadens with special reference to the nucleus and helical ribonucleoprotein bodies.

Abstract: SYNOPSIS. Previous reports on electron microscopy of Entamoeba invadens have been based on organisms grown in bacterized cultures; this is the first electron microscope study of amoebae grown axenically. The amoeba is bounded by a plasma membrane about 120 A wide bearing an externally fuzzy layer approximately 280 A thick. The major components of the cytoplasm are vacuoles of various sizes measuring 0.2 μ to 3.0 μ in diameter. These vacuoles are structureless, of low density and have a definite limiting membrane of the same thickness and density as the plasma membrane, suggesting their origin from the limiting membrane by pinocytosis. Neither mitochondria nor Golgi apparatus are present. The endoplasmic reticulum is poorly developed. The ground substance of the cytoplasm consists of two types of particles: smaller ones about 200–300 A of lower density and larger ones about 400–700 A of high density. The latter probably represent glycogen particles. The most important cytoplasmic organelles are the chromatoid bodies, composed of RNA and protein. These structures consist of parallel lamellae, each formed from coiled helical fibrils. The significance and possible relationship to protein synthesis are discussed. The nuclear membrane is double and there are a few discontinuities which may represent pores. It also shows the honeycomb structure found in other amoebae. The chromatin lies just beneath the nuclear membrane. Of special importance is the presence of intranuclear vesicles scattered within the chromatin layer. The endosome or nucleolus lies in the center of the nucleus.